title: Oligomerization is a key step in Cyt1Aa membrane insertion and toxicity but not necessary to synergize Cry11Aa toxicity in Aedes aegypti larvae.
abstract: Bacillus thuringiensis produces insecticidal Cry and Cyt proteins that are toxic to different insect orders. In addition, Cyt toxins also display haemolytic activity. Both toxins are pore-forming proteins that form oligomeric structures that insert into the target membrane to lyse cells. Cyt toxins play an important role in mosquitocidal activity since they synergize Cry toxins and are able to overcome resistance to Cry toxins. Cry and Cyt toxins interact by specific epitopes, and this interaction is important to induce the synergistic activity observed. It was proposed that Cyt toxins do not interact with protein receptors but directly interacting with the specific midgut cell lipids. Here, we analysed if oligomerization and membrane insertion of Cyt1Aa are necessary steps to synergize Cry11Aa toxicity. We characterized Cyt1Aa helix α-C mutants that were affected in oligomerization, in membrane insertion and also in haemolytic and insecticidal activities. However, these mutants were still able to synergize Cry11Aa toxicity indicating these steps are independent events of Cyt1Aa synergistic activity. Furthermore, the data indicate that formation of stable Cyt1Aa-oligomeric structure is a key step for membrane insertion, haemolysis and insecticidal activity.
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo Postal 510-3, Cuernavaca, Morelos 62250, Mexico.
authors.forename: Jazmin A
authors.initials: JA
authors.lastname: López-Diaz
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca, Morelos, 62250, Mexico.
authors.forename: Pablo Emiliano
authors.initials: PE
authors.lastname: Cantón
authors.affiliation: Department of Cell Biology and Neuroscience, University of California, Riverside, CA, 92521, USA.
authors.forename: Sarjeet S
authors.initials: SS
authors.lastname: Gill
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca, Morelos, 62250, Mexico.
authors.forename: Mario
authors.initials: M
authors.lastname: Soberón
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca, Morelos, 62250, Mexico.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Bravo
mesh_terms: D000330:Aedes / Q000187:drug effects*; D000818:Animals; D001413:Bacillus thuringiensis; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D002462:Cell Membrane / Q000737:chemistry; D004731:Endotoxins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D006460:Hemolysin Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D006461:Hemolysis; D053878:Hemolytic Agents / Q000737:chemistry / Q000494:pharmacology*; D007306:Insecticides / Q000737:chemistry / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects; D017433:Protein Structure, Secondary
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D053878:Hemolytic Agents; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis